As a vehicle approaches a landing, parking, or docking zone, the pilot or vehicle operator must begin to position the vehicle for landing, parking, or docking. As used herein the term "landing zone" refers to any type of landing, parking or docking zone, including but not limited to, airport runways and taxiways, off-shore platform landing zones, oil pipeline work landing zones, military landing zones, shipboard landing zones, helicopter operation landing zones, helipads, marine docks, aircraft parking docks, spacecraft docks, or any other type of landing, parking, or docking zone for a vehicle. Furthermore, as used herein, the term "pilot" refers to any type of vehicle pilot or operator of a vehicle.
Various systems exist which provide information to the pilot of a vehicle to assist in finding and entering the appropriate approach position, or "approach corridor," for a landing zone. An approach corridor is a landing zone approach area of space bounded generally by edges of demarcation which are determined by the type of vehicle being piloted and the physical shape and location of the landing zone. An approach corridor may extend upwardly from the ground or body of water and indefinitely in any direction or angle outward from a landing zone.
Approach corridor information may be supplied to the pilot of a vehicle by ground-based radar systems, radio frequency systems, ground communication lines, laser guidance systems, aircraft-mounted global positioning systems, satellite global positioning systems, or visual ground lighting systems, either alone or in combination with each other. The selection of an appropriate vehicular guidance system depends on the size, location, environment, etc., of the landing zone and the type of vehicle typically landing, parking, or docking at the particular landing zone.
Most existing guidance systems are expensive and/or difficult to install or maintain. Furthermore, the cost of an existing ground-based guidance system includes not only the system hardware and maintenance, but the cost of the real estate required for the system. For example, many current approach guidance systems cost in excess of one million dollars and the installation costs may be substantially higher if the guidance system is a ground-based system located in high-cost real estate areas or over water approaches.
Guidance systems which use ground-based lights to orient an approaching vehicle to a landing zone often include threshold lights. In general, current landing zone threshold lights are standard horizontal filament electric lamps covered by a weatherproof two-color lens made of glass or plastic. The lens resembles an inverted bottle which is either all red or is split vertically, half red, half green. The split lens is designed to emit red light toward an aircraft landing zone (to identify the landing zone end to a braking vehicle) and green light toward the vehicle making an approach (to identify the landing zone threshold over which the vehicle must pass before touch down).